Forklift

ABSTRACT

A forklift includes: a fork  22 , a moving mechanism configured to move the fork in a first direction; a laser sensor  20  mounted on the fork, configured to scan laser light in a second direction intersecting the first direction, and measure a distance from the laser sensor to a surrounding object based on reflection of the scanned laser light; and a processor configured to generate a three-dimensional range image within an emission range to which the laser light is emitted based on distance data acquired when the laser sensor scans the laser light in the second direction while the moving mechanism moves the fork in the first direction.

TECHNICAL FIELD

The present application claims priority based on Japanese PatentApplication No. 2015-097487 filed on May 12, 2015, the contents of whichare hereby incorporated by reference into the present application. Thetechnique disclosed herein relates to a forklift.

BACKGROUND

In a load-lifting operation using a forklift, interferences between afork and a pallet need to be avoided. In a forklift described inJapanese Patent Application Publication No. 2005-89013, a reflectiveoptical sensor detects upper and lower ends of an opening of a pallet.Then, a clearance between an upper surface of a fork and the upper endof the opening of the pallet and a clearance between a lower surface ofthe fork and the lower end of the opening of the pallet are calculated,and a fork position is adjusted so that these clearances takeappropriate values.

SUMMARY

To perform an accurate load-lifting operation with a forklift,identification accuracy of a pallet position needs to be improved.However, despite being capable of detecting a heightwise displacement ofa pallet, the conventional technique had been unable to detect a lateraldisplacement and a displacement related to rotation.

The present description discloses a forklift that enables detection of alateral positional displacement and a displacement related to rotationof a pallet using a simple configuration.

A forklift disclosed herein may comprise: a fork; a moving mechanismconfigured to move the fork in a first direction; a laser sensor mountedon the fork, configured to scan laser light in a second directionintersecting the first direction, and measure a distance from the lasersensor to a surrounding object based on reflected light of the scannedlaser light; and a processor configured to generate a three-dimensionalrange image within an emission range to which the laser light is emittedbased on distance data acquired when the laser sensor scans the laserlight in the second direction while the moving mechanism moves the forkin the first direction.

In the above forklift, the laser sensor is mounted on the fork, andthus, when the fork moves in the first direction, the laser sensor movesin the first direction together therewith. Due to this, even if thelaser sensor is of a one-dimensional scan type that scans the laserlight in the second direction, the laser sensor can scan the laser lightin the first and second directions by the motion of the fork in thefirst direction. Due to this, a three-dimensional range image can beacquired by using the laser sensor. This forklift is capable ofacquiring the three-dimensional range image, so a positionaldisplacement in a lateral direction and a displacement related torotation of the pallet can be detected.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a schematic configuration of aforklift of an embodiment.

FIG. 2 is a diagram schematically showing a state in which laser lightis scanned by the forklift of the embodiment.

FIG. 3 is a block diagram showing a control system of the forklift ofthe embodiment.

FIG. 4 is a flowchart showing procedures of a process of acquiring athree-dimensional range image using a laser sensor.

FIG. 5 is a diagram showing a state in which distance data from thelaser sensor to a pallet is being acquired by the laser sensor.

FIG. 6 is a flowchart showing procedures of a process of identifying aposition, orientation, and width of the pallet.

FIG. 7 is a diagram for explaining a method of detecting openings of thepallet.

FIG. 8 is a diagram for explaining a method of calculating a length of apoint group configuring a straight line extracted from acquiredthree-dimensional distance data.

FIG. 9 is a diagram showing the pallet and coordinate axes set to thepallet together.

FIG. 10 is a diagram schematically showing a state in which laser lightis scanned by using a tilting mechanism configured to tilt a fork.

FIG. 11 is a diagram for explaining a process of identifying a palletfront face from the three-dimensional range image.

DETAILED DESCRIPTION

Some of the features of embodiments described below will be listed. Itshould be noted that the respective technical features described beloware independent of one another, and useful solely or in combinations.The combinations thereof are not limited to those described in theclaims as originally filed.

(Feature 1) In a forklift disclosed herein, a moving mechanism maycomprise at least a lifting mechanism configured to move a fork up anddown in a vertical direction, and a laser sensor may move up and down inthe vertical direction as the fork moves up and down in the verticaldirection. According to such a configuration, the lifting mechanism thatmoves the fork up and down in the vertical direction can be used tovertically scan light emitted from the laser sensor.

(Feature 2) In a forklift disclosed herein, the moving mechanism maycomprise at least a tilting mechanism configured to tilt a distal end ofthe fork with respect to a proximal end of the fork, and the laser lightemitted from the laser sensor may be scanned in the vertical directionas the distal end of the fork tilts with respect to the proximal end ofthe fork. According to such a configuration, the tilting mechanism thattilts the fork can be used to vertically scan the light emitted from thelaser sensor.

(Feature 3) In a forklift disclosed herein, when a generatedthree-dimensional range image includes a pallet, a processor may beconfigured to identify a position, an orientation, and a width of apallet based on the three-dimensional range image. According to such aconfiguration, the three-dimensional position, orientation, and width ofthe pallet are identified based on the three-dimensional range imagegenerated from the distance data acquired by the laser sensor, so apositional displacement in a lateral direction and a displacementrelated to rotation of the pallet can accurately be detected.

(Feature 4) In a forklift disclosed herein, when the generatedthree-dimensional range image includes the pallet, the processor may beconfigured to selectively extract only distance data acquired from afront face of the pallet from the three-dimensional range image andidentify the position, the orientation, and the width of the palletbased on a plane at the front face of the pallet identified based on theextracted distance data. According to such a configuration, thethree-dimensional position, orientation, and width of the pallet areidentified based on the distance data acquired from the front face ofthe pallet that was extracted from the three-dimensional range imagegenerated from the distance data acquired by the laser sensor. Sincepositional information of the pallet is identified from the distancedata acquired from the front face of the pallet, the positionaldisplacement in the lateral direction and the displacement related torotation of the pallet can accurately be detected.

First Embodiment

With reference to the drawings, a forklift 10 of the present embodimentwill be described. As shown in FIG. 1, the forklift 10 is an unmannedforklift, and includes a vehicle body 12, a mast 24, a fork 22, a liftchain 26, a laser sensor 20, and a controller 30.

The vehicle body 12 is provided with a front wheel 28 and a rear wheel29 at each of its lateral surfaces. The front wheels 28 and the rearwheels 29 are supported rotatably on the vehicle body 12. One of therear wheels 29 is connected to a driving motor that is not shown, and isconfigured to be driven to rotate by the driving motor. Further, therear wheel 29 connected to the driving motor is also connected to asteering device that is not shown, and an orientation of the wheel isadjusted by the steering device. The other of the rear wheels 29 is acaster wheel, and is rotated and steered by following motions of thevehicle body 12. The controller 30 controls the driving motor and thesteering device to allow the vehicle body 12 to run on a road and tochange a moving direction of the vehicle body 12.

The mast 24 is a post mounted to a front surface of the vehicle body 12,and its axis extends in a vertical direction. The fork 22 is mounted tothe mast 24 by being able to move in the vertical direction. Further,the fork 22 is configured capable of swinging with respect to the mast24 by a tilting mechanism that is not shown. The fork 22 includes a pairof tines 22 a, 22 b. The tines 22 a, 22 b are disposed at positionsspaced apart from each other in a right-and-left direction of thevehicle body 12, and extend forward of the vehicle body 12 from a mast24 side. The lift chain 26 is disposed on the mast 24, and is engagedwith the fork 22. When the lift chain 26 is driven by a fork liftingdevice 40 (shown in FIG. 3), the fork 22 is lifted and lowered accordingto a motion of the lift chain 26. A position of the fork 22 in thevertical direction can be identified by a driving amount of the forklifting device 40.

The laser sensor 20 is mounted to the fork 22, and is lifted and loweredin the vertical direction together with the fork 22. A position to whichthe laser sensor 20 is mounted is between the tine 22 a and the tine 22b, and on a backward side (on a vehicle body 12 side) relative to abackrest surface of the fork 22. The laser sensor 20 is aone-dimensional scanning-type laser sensor that scans the laser light inone direction (the horizontal direction in the present embodiment). Thelaser sensor 20 emits the laser light, and measures a distance to itssurrounding object using reflection of the emitted laser light. Sincethe laser sensor 20 moves up and down according to an up and down motionof the fork 22, a heightwise position of the laser light emitted fromthe laser sensor 20 changes according to the motion. In the presentembodiment, as shown in FIG. 2, the laser sensor 20 emits the laserlight to a region 50 (see FIG. 1) having a predetermined angular rangeand set forward of the forklift 10, while lifting and lowering in thevertical direction. Due to this, the laser light emitted from the lasersensor 20 is scanned in the horizontal direction and in a heightdirection (two-dimensionally), and distance data 41 of a range setforward of the forklift 10 is thereby acquired. Three-dimensionaldistance data acquired by the laser sensor 20 is inputted into thecontroller 30 (see FIG. 3).

It should be noted that, UTM-30LX made by HOKUYO AUTOMATIC CO. LTD,LMS100 made by SICK AG, or the like may for example be used as the lasersensor 20.

The controller 30 is constituted of a microprocessor provided with a CPUand the like. The controller 30 is installed in the vehicle body 12. Thecontroller 30 is connected to the laser sensor 20, the driving motorthat drives the one of the rear wheels 29, the steering device thatadjusts the steering angle of the rear wheel 29 connected to the drivingmotor, the fork lifting device that lifts and lowers the fork 22, andthe like as aforementioned, and controls operations thereof.

That is, the controller 30 performs a process to lift and lower thelaser sensor 20, a process to perform coordinate conversion on thedistance data, and a process to store coordinate-convertedthree-dimensional distance data to generate a three-dimensional rangeimage by executing a program stored in a memory. Further, the controller30 performs a process to identify a position, an orientation, and awidth of a pallet 100 based on the three-dimensional range image, andthe like. That is, as shown in FIG. 3, the controller 30 functions as acoordinate converting unit 32, a calculating-storing unit 34, a palletidentifying unit 36, a sensor movement controlling unit 38, and a sensorposition detecting unit 39. A three-dimensional range image 44 of asurrounding object in a space set forward of the forklift 10 isgenerated by the controller 30 functioning as the aforementionedrespective units 32 to 39, and further the position, orientation, andwidth of the pallet 100 are identified from the generatedthree-dimensional range image 44. Details of the respective units 32 to39 will be described together with processes executed by the controller30 described later.

Next, a process to generate three-dimensional distance data 42 by thecontroller 30 will be described. The three-dimensional distance datagenerating process is performed in a state where the forklift 10 is instandby in a vicinity of the pallet 100 to be lifted. That is, as shownin FIG. 4, the controller 30 firstly drives one of the rear wheels 29and moves the forklift 10 to approach the pallet 100 so that the pallet100 is located in front of the vehicle body 12. That is, the forklift 10is moved to an initial position in front of the pallet to observe thepallet 100 using the laser sensor 20 (S10). For example, the forklift 10that conveys loads within a factory has preset positions for lifting theloads (the pallet 100). Due to this, the initial position for theforklift 10 to be in standby is preset with respect to the positionwhere the pallet 100 is to be lifted. Due to this, the controller 30causes the forklift 10 to move autonomously to the preset 26 initialposition. It should be noted that, in a case where the forklift 10 is tobe driven by a driver personnel, the forklift 10 may be moved to theinitial position by the driver personnel, and thereafter thethree-dimensional distance data generating process may be started by aswitch operation by the driver personnel on the forklift 10.

Next, the controller 30 moves the laser sensor 20 by using the forklifting device 40 so that the laser light is emitted to an upper limitof a target observation region 60 (shown in FIG. 5) (S12). The targetobservation region 60 is a region where the pallet 100 may be existing.For example, as shown in FIG. 5, in a case where a package 130 ismounted on the pallet 100, and the pallet 100 is mounted on a stage 120,the region where the pallet 100 may be existing (height and widththereof) is determined by sizes of the stage 120 and the pallet 100. Instep S12, the laser sensor 20 is moved to the upper limit of the regionwhere the pallet 100 may be existing, so that the pallet 100 can surelybe detected.

Next, the controller 30 acquires distance data 41 using the laser sensor20 while lowering the fork 22 using the fork lifting device 40 (S14).That is, the laser sensor 20 scans and emits the laser light along thehorizontal direction, while at the same time detects reflection of theemitted laser light. On the other hand, since the fork lifting device 40lifts and lowers the fork 22, the laser sensor 20 moves in the verticaldirection. Due to this, the laser light emitted from the laser sensor 20is scanned in a vertical direction as well. Accordingly, in the processof step S14, the laser light from the laser sensor 20 is scanned in boththe horizontal and vertical directions, and detection of the reflectionsthereof allows an acquisition of observation point groups in the targetobservation region 60. It should be noted that, a function of thecontroller 30 realized by the aforementioned processes of steps S12 andS14 corresponds to the sensor moving controlling unit 38 shown in FIG.3.

Next, the controller 30 converts the acquired distance data 41 tothree-dimensional distance data 42 in which a height of the laser sensor20 is reflected (S16). That is, since the controller 30 controls thefork lifting device 40 to lift and lower the fork 22, a position of thefork 22 in the vertical direction (a heightwise position of the lasersensor 20) can be identified. Due to this, when reflection is opticallyreceived in the laser sensor 20, the controller 30 reflects heightinformation of the laser sensor 20 at the time of the optical receptionto the distance data 41 (at the observation point) and converts it tothe three-dimensional distance data 42. Due to this, thethree-dimensional distance data 42 indicative of the object existing inthe region 50 having the predetermined angular range where the laserlight was emitted can be acquired. It should be noted that a function ofthe controller 30 realized by the process of step S16 as abovecorresponds to the coordinate converting unit 32 and the sensor positiondetecting unit 39 shown in FIG. 3.

Next, the controller 30 selectively extracts only an observation pointgroup within the target observation region 60 from the acquiredthree-dimensional distance data 42, and stores the same in the memory(S18). Since the height of the laser sensor 20 is reflected in thethree-dimensional distance data 42, the observation point group in thetarget observation region 60 at that height is stored in the memory. Itshould be noted that a function of the controller 30 realized by theprocess of step S18 as above corresponds to the calculating-storing unit34 shown in FIG. 3.

Next, the controller 30 determines whether or not a current observingposition (height) by the laser sensor 20 is at a lower limit of thetarget observation region 60 (S20). If it is determined that the currentobserving position is not at the lower limit of the target observationregion (NO to S20), the controller 30 repeats the processes of steps S14to S18. It should be noted that, if it is determined that the currentobserving position is at the lower limit of the target observationregion (YES to S20), the controller 30 completes the process.

By repeatedly performing the aforementioned processes, the observationpoint groups (three-dimensional distance data 42) for an entirety of thetarget observation region 60 can be stored in the memory, as a result ofwhich the three-dimensional range image 44 in the target observationregion 60 can thereby be generated.

Next, the process of identifying the position, orientation, and width ofthe pallet 100 will be described with reference to FIGS. 6 and 7.Firstly, the controller 30 drives the one of the rear wheels 29 to causethe forklift 10 to approach the pallet 100 so that the pallet 100 islocated in front of the vehicle body 12. That is, the controller 30moves the forklift 10 to the initial position in front of the pallet soas to observe the pallet 100 using the laser sensor 20 (S22). Next, thecontroller 30 moves the laser sensor 20 by using the fork lifting device40 so that the laser light is emitted to an upper limit of the targetobservation region 60 (shown in FIG. 5) (S24). Next, the controller 30acquires distance data 41 using the laser sensor 20 while lowering thefork 22 using the fork lifting device 40 (S26). Then, the controller 30converts the acquired distance data 41 to three-dimensional distancedata 42 in which the height of the laser sensor 20 is reflected (S28).It should be noted that, since the processes of steps S22 to S28 aresame as the processes of steps S10 to S16 as aforementioned, thedetailed description thereof will be omitted.

Next, the controller 30 selectively extracts the observation point groupin the target observation region 60 from the three-dimensional distancedata 42, and a straight line extending in a substantially horizontaldirection is extracted from the observation point group that has beenextracted (S30). As shown in FIG. 7, the observation point groupconstituted of reflection that is reflected on the front face of thepallet 100 is located on a single plane. That is, in step S30, thestraight line, which is a resultant from scanning the front face of thepallet 100, is extracted from the observation point group. It should benoted that, the extraction of the straight line can use well-knownalgorithms called robust estimation, such as RANSAC.

Next, the controller 30 clusters the point group constituting theextracted straight line (matching the straight line) by using Euclideandistances (S32). Here, as shown in FIGS. 5 and 7, the front face of thepallet 100 has two openings 110 (into which the tines 22 a, 22 b of thefork 22 are to be inserted). Due to this, the straight line extractedfrom the front face of the pallet 100 may be divided by the openings 110in the front face of the pallet 100. Thus, a determination on whether ornot the straight line is extracted from a single object (for example,from the front face of the pallet 100) is made using Euclidean distancesin the point group constituting the straight line extracted in step S30.It should be noted that, for this clustering, well-known methods such ask-means method or kd-tree method may be used.

Next, the controller 30 performs a process of step S34. Specifically,the controller 30 firstly counts a number of straight line groups thathad been clustered (that is a number of clusters), and determineswhether or not the counted number of clusters is three (S34). Asaforementioned, at a position (height) in the front face of the pallet100 where the openings 110 are provided, the straight line extending inthe substantially horizontal direction (the observation point group) isdivided into three by the openings 110 in a laser light horizontal scan(YES to S34). Accordingly, in step S34, a determination can be made onwhether or not the extracted straight line corresponds to the front faceof the pallet 100 by determining the cluster number is three or not.

Next, the controller 30 determines whether or not a length of the pointgroup configuring the straight line extracted in step S30 issubstantially equal to the width of the pallet 100 (S34). Here, astandard of the pallet 100 is normally known in advance. Thus, adetermination can be made on whether or not the straight line on thefront surface of the pallet 100 is being extracted by comparing thelength of the point group configuring the extracted straight line and apreset value (a value set from the standard of the pallet 100). A lengthW_(p) of the point group configuring the extracted straight line may beobtained by using observation points having maximal and minimal valuesalong an x direction and maximal and minimal values along a y directionwithin the point group as for example shown in FIG. 8. The controller 30determines whether or not the obtained length is equal to the width ofthe pallet 100 by comparing it with the width of the pallet 100 (presetvalue).

In the process of step S34 as aforementioned, if one or more of theconditions are not met (NO to S34), the controller 30 terminates theprocess on the point group constituting the extracted straight line, andproceeds to a process of step S38. If all of the conditions in the 265process of step S34 are met (YES to S34), the controller 30 stores thepoint group constituting the straight line as data that was obtained byobserving the front face of the pallet 100 (S36).

Next, the controller 30 determines whether or not a current observingposition (height) of the laser sensor 20 is at a lower limit of thetarget observation region 60 (S38). Since the controller 30 controls thefork lifting device 40 to lift and lower the fork 22, it is capable ofidentifying a position of the fork 22 in the vertical direction. Sincethe laser sensor 20 is mounted on the fork 22, the controller 30 (thesensor position detecting unit 39 shown in FIG. 3) is capable ofidentifying a heightwise position of the laser sensor 20. If the currentobserving position (height) is at the lower limit of the targetobservation region 60 (YES to S38), the controller 30 identifies aposition, orientation, and width of the pallet 100 from the storedobservation point group (the three-dimensional range image 44, which mayhereinbelow be termed a convoluted point group) (S40). That is, astraight line group having the cluster number of three, and in which alength of the point group constituting the straight line was determinedas being equal to the width of the pallet 100 is obtained from aheightwise range of the front face of the pallet 100 where the openings110 are provided. In step S40, the position, orientation, and width ofthe pallet 100 are identified using the data of the observation pointgroup constituting such a straight line group. A process of step S40will be described in detail below. It should be noted that, if thecurrent observing position (height) is not at the lower limit of thetarget observation region 60 (NO to S38), the controller 30 returns tothe process of step S24.

Next, a method of identifying the position, orientation, and width ofthe pallet 100 in step S40 will be described. Firstly, avariance-covariance matrix as in the following formula (1) will beconsidered to obtain main axes (that is, an x axis, a y axis, and a zaxis shown in FIG. 9) from variations of respective points (x_(i),y_(i), z_(i)) (i=1 to N) in N sets of convoluted point groups.

$\begin{matrix}{\left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack \mspace{661mu}} & \; \\{\frac{1}{N}{\sum\limits_{i}^{N}\begin{pmatrix}\left( {x_{i} - \overset{\_}{x}} \right)^{2} & {\left( {x_{i} - \overset{\_}{x}} \right)\left( {y_{i} - \overset{\_}{y}} \right)} & {\left( {x_{i} - \overset{\_}{x}} \right)\left( {z_{i} - \overset{\_}{z}} \right)} \\{\left( {x_{i} - \overset{\_}{x}} \right)\left( {y_{i} - \overset{\_}{y}} \right)} & \left( {y_{1} - \overset{\_}{y}} \right)^{2} & {\left( {y_{i} - \overset{\_}{y}} \right)\left( {z_{i} - \overset{\_}{z}} \right)} \\{\left( {x_{i} - \overset{\_}{x}} \right)\left( {z_{i} - \overset{\_}{z}} \right)} & {\left( {y_{i} - \overset{\_}{y}} \right)\left( {z_{i} - \overset{\_}{z}} \right)} & \left( {z_{i} - \overset{\_}{z}} \right)^{2}\end{pmatrix}}} & (1)\end{matrix}$

In the above formula (1), an x bar, a y bar, and a z bar respectivelyrepresent averages of coordinates of N sets of points x_(i), y_(i),z_(i), and represent a center of the front face of the pallet 100.

Next, an eigenvector in a three-dimensional space is calculated fromthis matrix. A first main axis of this eigenvector corresponds to avector of the pallet in a lateral side face direction (the y axis inFIG. 9), a second main axis corresponds to a vector of the pallet in atop face direction (the z axis in FIG. 9), and a third main axiscorresponds to a normal vector of the front face of the pallet (the xaxis in FIG. 9). According to this, the position and orientation of thepallet in a coordinate system defining its origin at the center of thefront face of the pallet are identified. It should be noted that, sincethe direction of the eigenvector representing the main axes may have itspositive and negative directions inverted depending on cases, it ispreferable to adjust signs thereof according to its relativerelationship with the laser sensor 20.

Here, a size and width of the pallet 100 can be obtained by projectingthe convoluted point group in a plane defined by the first and secondmain axes of the aforementioned eigenvector. Specifically, a differencebetween maximal and minimal values of the projection on the first mainaxis (y axis) corresponds to the width of the pallet 100, and adifference between maximal and minimal values of the projection on thesecond main axis (z axis) corresponds to a heightwise dimension of theopenings 110 of the pallet 100. That is, the size and width of thepallet 100 can thereby be identified. Due to this, the position,orientation, and width of the pallet 100 can be identified. Further,averages of the maximal values and the minimal values of the respectiveprojections of the convoluted point group to respective planes definedby the first, second, and third main axes may be set as the center pointof the pallet 100. It should be noted that a function of the controller30 realized by the above process of step S40 corresponds to the palletidentifying unit 36 shown in FIG. 3.

In the forklift 10 of the aforementioned embodiment, the laser sensor 20is mounted to the fork 22. Due to this, the laser sensor 20 moves up anddown as the fork 22 moves up and down. As such, the three-dimensionalrange image of the pallet 100 can be acquired simply by allowing thelaser sensor 20 to scan the laser light in the horizontal directionwhile moving the fork 22 up and down. Further, since the position,orientation, and width of the pallet 100 are identified using thethree-dimensional range image of the pallet 100, a positionaldisplacement in a lateral direction and a displacement related torotation of the pallet 100 can be detected. As a result, interferencebetween the fork 22 and the pallet 100 can be prevented, and smoothloading operation is thereby enabled.

Further, in the forklift 10 of the present embodiment, a determinationcan be made on whether or not a load is mounted on the pallet 100 usingthe laser sensor 20, and further, a position of the load on the pallet100 can be identified. Due to this, it can be recognized in advance ifthe load is mounted on the pallet 100 at an unbalanced position, sopreventive measures can be taken against the load falling off of thepallet 100. Further, since a shape of the load on the pallet 100 can beidentified, a type of the load can also be identified.

Finally, corresponding relationships between the aforementionedembodiment and the claims will be described. The fork lifting device 40is an example of “moving mechanism” in the claims, and thecalculating-storing unit 34 and the pallet identifying unit 36 are anexample of “processor” in the claims.

The embodiments have been described in detail, however, these are mereexemplary indications and thus do not limit the scope of the claims. Theart described in the claims include modifications and variations of thespecific examples presented above.

For example, in the present embodiment, the laser light is scanned inthe vertical direction by moving the fork up and down in the verticaldirection, however, the technique disclosed herein is not limited tothis configuration. For example, as shown in FIG. 10, the laser lightemitted from the laser sensor 20 may be scanned in the verticaldirection by using a tilting mechanism that tilts a distal end of thefork with respect to its proximal end.

Further, in the present embodiment, the pallet 100 is detected byextracting straight lines from the observation point groups obtainedusing the laser sensor 20, however, the technique disclosed herein maydirectly extract a plane of the front face of the pallet 100 from theobservation point groups obtained using the laser sensor 20. Forexample, as shown in FIG. 11, when the pallet 100 is directly placed ona floor surface G and a load 130 is mounted on the pallet 100, a frontface of the load 130 (plane 1), the front face of the pallet 100 (plane2), and the floor surface G (plane 3) may be extracted using the lasersensor 20. Due to this, the position, orientation, and width of thepallet 100 can be identified by performing the process of step S40 shownin FIG. 6 on the observation point groups constituting the front face ofthe pallet 100 (plane 2). It should be noted that for the planeextraction, the RANSAC algorithm can be used similar to the straightline extraction in step S30 of FIG. 6.

Technical features described in the description and the drawings maytechnically be useful alone or in various combinations, and are notlimited to the combinations as originally claimed. Further, the artdescribed in the description and the drawings may concurrently achieve aplurality of aims, and technical significance thereof resides inachieving any one of such aims.

1. A forklift comprising: a fork; a moving mechanism configured to movethe fork in a first direction; a laser sensor mounted on the fork,configured to scan laser light in a second direction intersecting thefirst direction, and measure a distance from the laser sensor to asurrounding object based on reflection of the scanned laser light; and aprocessor configured to generate a three-dimensional range image withinan emission range to which the laser light is emitted based on distancedata acquired when the laser sensor scans the laser light in the seconddirection while the moving mechanism moves the fork in the firstdirection.
 2. The forklift according to claim 1, wherein the movingmechanism comprises at least a lifting mechanism configured to move thefork up and down in a vertical direction, and the laser sensor moves upand down in the vertical direction as the fork moves up and down in thevertical direction.
 3. The forklift according to claim 1, wherein themoving mechanism comprises at least a tilting mechanism configured totilt a distal end of the fork with respect to a proximal end of thefork, and the laser light emitted from the laser sensor is scanned inthe vertical direction as the distal end of the fork tilts with respectto the proximal end of the fork.
 4. The forklift according to claim 1,wherein when the generated three-dimensional range image includes apallet, the processor is configured to identify a position, anorientation, and a width of the pallet based on the three-dimensionalrange image.
 5. The forklift according to claim 4, wherein when thegenerated three-dimensional range image includes the pallet, theprocessor is configured to selectively extract only distance dataacquired from a front face of the pallet from the three-dimensionalrange image and identify the position, the orientation, and the width ofthe pallet based on a plane at the front face of the pallet identifiedbased on the extracted distance data.